Film buffs might find something curiously familiar in a 1918 engraving by the artist Christopher Nevinson, showing four Tommies perched up a telegraph pole rigging communication lines: Lord Attenborough recreated the image virtually line by line in his classic 1969 film, Oh What a Lovely War.

Years later he bought the print, along with other haunting first world war images by the artist, adding to a remarkable collection that the director and his wife, the actor Sheila Sims, began almost 60 years ago when they bought the house on Richmond Green that is still their home.

They bought the first pictures when they couldn't afford carpets or curtains for most of the rooms. Now they say they have run out of walls. And so 51 paintings and prints, including works by Sickert – the only painting with an obvious theatrical connection, depicting a natty Victorian gent on the stage of the Middlesex music hall – Henry Moore, Barbara Hepworth and Ben Nicholson, are to be auctioned at Sotheby's next week, with a total estimated value of more than £2m.

"You could certainly call it a dense hang," said James Rawlin, head of 20th-century British art at Sotheby's, who first saw the pictures in Attenborough's home. "To be honest I think they ran out of walls years ago. We have by no means stripped the house, they have lots of good things left."

The couple are selling Christopher Wood's 1922 heavily Cezanne-influenced Card Players for the second time. They bought it in 1949 and sold it at Christie's in 1980 when Attenborough was desperately trying to raise the money to make his award-winning biopic Gandhi. They bought it back five years later, and it is now estimated at up to £50,000.

Attenborough also bought a painting by Matthew Smith from his friend John Mills when the latter was broke, but allowed it to stay Mills's walls until his death.

The Attenboroughs knew many of the artists personally, and on one occasion offered a lift in the rain to a shabbily dressed man who seemed uncertain of his welcome at the Tate gallery. They waited to make sure he was all right, but the man reappeared a minute later, explaining dolefully: "I don't think they know who I am." A painting by the shabby man, LS Lowry's Old Houses, is included in the sale, estimated at up to £500,000.

Rawlin is not sure the Attenborough walls will remain uncluttered: "The real collectors just can't give up: they try, but then they see something and they have to have it."